Excess mortality and shortened life expectancy in people with major mental illnesses in Taiwan

Abstract

Aims: Given the concerns of health inequality associated with mental illnesses, we aimed to reveal the extent of which general mortality and life expectancy at birth in people with schizophrenia, bipolar disorder and depressive disorder varied in the 2005 and 2010 nationally representative cohorts in Taiwan.

Methods: Two nationally representative samples of individuals with schizophrenia, bipolar disorder and depressive disorder were identified from Taiwan's national health insurance database in 2005 and 2010, respectively, and followed-up for consecutive 3 years. The database was linked to nationwide mortality registry to identify causes and date of death. Age-, gender- and cause-specific mortality rates were generated, with the average follow-up period of each age- and gender-band applied as 'weighting' for the calculation of expected number of deaths. Age- and gender-standardised mortality ratios (SMRs) were calculated for these 3-year observation periods with Taiwanese general population in 2011/2012 as the standard population. The SMR calculations were then stratified by natural/unnatural causes and major groups of death. Corresponding life expectancies at birth were also calculated by gender, diagnosis of mental disorders and year of cohorts for further elucidation.

Results: The general differential in mortality rates for people with schizophrenia and bipolar disorder remained wide, revealing an SMR of 3.65 (95% confidence interval (CI): 3.55-3.76) for cohort 2005 and 3.27 (3.18-3.36) for cohort 2010 in schizophrenia, and 2.65 (95% CI: 2.55-2.76) for cohort 2005 and 2.39 (2.31-2.48) for cohort 2010 in bipolar disorder, respectively. The SMRs in people with depression were 1.83 (95% CI: 1.81-1.86) for cohort 2005 and 1.59 (1.57-1.61) for cohort 2010. SMRs due to unnatural causes tended to decrease in people with major mental illnesses over the years, but those due to natural causes remained relatively stable. The life expectancies at birth for schizophrenia, bipolar disorder and depression were all significantly lower than the national norms, specifically showing 14.97-15.50 years of life lost for men and 15.15-15.48 years for women in people with schizophrenia.

Conclusions: Compared to general population, the differential in mortality rates for people with major mental illnesses persisted substantial. The differential in mortality for unnatural causes of death seemed decreasing over the years, but that due to natural causes remained relatively steady. Regardless of gender, people with schizophrenia, bipolar disorder and depression were shown to have shortened life expectancies compared to general population.

Keywords: bipolar disorder; depression; excess mortality; life expectancy at birth; schizophrenia; standardised mortality ratio.

Fig. 1.

Standardised mortality ratios for people with schizophrenia, bipolar disorder or depression disorder in Taiwan by gender in 2005/2010 cohorts.